Use non-throwing is_directory in filesystem::create_directory

The create_dir helper was calling the throwing form of
filesystem::is_directory instead of passing the error_code argument.
Since std::filesystem::create_directory(const path&, error_code&) is
noexcept, it would call std::terminate if an error occurred in
is_directory.

Passing the error_code also takes care of clearing it in the case where
is_directory returns true.

	src/filesystem/ops.cc (create_dir): Pass error_code to is_directory.
	src/filesystem/std-ops.cc (create_dir): Likewise.

From-SVN: r258375

libstdc++-v3/ChangeLog

+2018-03-09  Jonathan Wakely  <jwakely@redhat.com>
+
+	src/filesystem/ops.cc (create_dir): Pass error_code to is_directory.
+	src/filesystem/std-ops.cc (create_dir): Likewise.
+
 2018-03-08  François Dumont  <fdumont@gcc.gnu.org>
 
 	* python/libstdcxx/v6/printers.py (NodeIteratorPrinter): New.

libstdc++-v3/src/filesystem/ops.cc

@@ -463,10 +463,8 @@ namespace
     if (::mkdir(p.c_str(), mode))
       {
 	const int err = errno;
-	if (err != EEXIST || !is_directory(p))
+	if (err != EEXIST || !is_directory(p, ec))
 	  ec.assign(err, std::generic_category());
-	else
-	  ec.clear();
       }
     else
       {

libstdc++-v3/src/filesystem/std-ops.cc

@@ -668,10 +668,8 @@ namespace
     if (::mkdir(p.c_str(), mode))
       {
 	const int err = errno;
-	if (err != EEXIST || !is_directory(p))
+	if (err != EEXIST || !is_directory(p, ec))
 	  ec.assign(err, std::generic_category());
-	else
-	  ec.clear();
       }
     else
       {